In parallel, a study of precipitate sizes was carried out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM

On the basis of steel 38MnSiVS5 a high number of castings were manufactured varying only the Ti and Al contents and obtaining ingots in which the Ti/Al ratio was different in each case. The specimens will be heated in air furnace to different austenitization temperatures, between 900°C and 1 200°C, and subsequently quenched in water. The most important achievement would be that Al plays a harmful role as an austenite grain controller at high temperatures (Ͼ1 050°C), as a consequence of the quick dissolution of AlN particles and therefore the reduction in inhibition forces at the grain boundaries which are intercepted by them. The best austenite grain control was shown by steel with contents of Tiϭ0.044, Alϭ0.009, Nϭ0.0131 (mass%) and a Ti/N ratio of 3.36. But the interpolation of the results allows it to be concluded that the best Ti/N ratio would be close to 2.5. It was also found that the control of austenite grain size improved with an addition of Nb. In paralell, a study of precipitate sizes was carried out using transmission electron microscopy (TEM) and scanning electron microscopy (SEM).

The simulation methodapplied to determine no-recrystallization temperature (T**) has also been used to simultaneously determine phasetransformation temperatures on cooling (A*3, A*1) in a set of six steels with different Ti and N contents. A study has been made of the influence of Ti and Ncontents on these parameters for different strain conditions, and the results permit an estimation of what would be the most appropriate contents depending on the type of rolling (hot strip mill, near net shape casting). Austenite grain size was also determined at 11 OO'Cand 1 300'C for all the steels, it being found that a Ti/N ratio close to two gave the finest grain,

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